Ultrasound of the bladder is used in clinical practice as a non-invasive estimate of bladder volume when assessing post-void urinary residual. Two types of ultrasound equipment are dedicated bladder scanner and standard linear array transabdominal or transvaginal ultrasound. Ultrasound of the bladder neck can be used to assess urethral hypermobility. Increased bladder neck mobility is associated with stress urinary incontinence. The volume of the urethral sphincter can be measured using three-dimensional ultrasound. Measurement of the thickness of the bladder wall has been validated using the transvaginal, transperineal, translabial or transabdominal approach. The ultrasound is likely to be used increasingly to provide the anatomical parameters in conjunction with functional parameters provided by urodynamics. Two-dimensional and three-dimensional ultrasounds have been employed to statically and dynamically image the pelvic floor. The application of ultrasound in the identification of levator injury is currently being used as a research tool.

Ultrasound has the advantage of being able to visualise fluid-filled structures without the need for contrast medium. It can demonstrate soft tissue structures such as the kidney, bladder wall, urethral and anal sphincters and surrounding pelvic floor musculature. Use of the transabdominal, transvaginal, transrectal and transperineal approaches for ultrasound scanning allows for easy visualisation of different aspects of the lower urinary tract. Bladder diverticula are easily visualised with transabdominal ultrasound. Transvaginal ultrasound allows clearer visualisation of the bladder base, bladder neck, inferior border of the pubic symphysis and periurethral structures. Translabial ultrasound is used to demonstrate uterovaginal prolapse. Three-dimensional ultrasound offers new insights into the pelvic floor as it allows imaging of both the levator ani muscle hiatus and paravaginal support structures in axial and transverse planes. This gives access to transverse planes similar to magnetic resonance imaging.